Re: [Jython-users] Question about compiling with Jython

[Jeff A. <ja...@fa...>]

Hi Ted.

Can you put the classpath at the end like that? Last thing is usually 
the class. Although why is java not complaining about main? Possibly it 
thinks HelloWorld$py is an inner class. Or is the $py being treated as a 
variable="" by the shell. It hardly matters: it still has to be a class 
that contains a main(), and one compiled from Python does not.If you 
want to see what it contains, you can javap it.

You can make a class you run like that, but you have to write it in 
Java, and reference the .py file, or maybe have the text of the program 
in there as a string. It would be something like this:

package demo_jython;

import org.python.util.PythonInterpreter;

public class ListDemo {

     public static void main(String[] args) {
         PythonInterpreter interp = new PythonInterpreter();
         interp.exec("print 6*7");
         interp.execfile("HelloWorld.py");
     }
}

You would then run that in the normal way for a Java program, except you 
need the dependencies on the path, say by putting the jython.jar or 
jython-standalone.jar on the class path.

Jeff Allen

On 30/09/2018 20:05, Ted Larson Freeman wrote:
> Hi, Jeff and Adam.
>
> Thanks for your replies. My goal is to see if I can produce a Java 
> .class file using Jython, which can then be run using Java on the 
> command line. A coworker was able to do this with Scala in less than 
> 15 minutes (including installation), and I wanted to see if I could do 
> the same thing with Jython. (I can run Jython itself with the script 
> below just fine.)
>
> I'm still missing something, as I get the same error with either the 
> CLASSPATH evironment variable or when explicitly setting it on the 
> command line. For example:
>
> % ls
> HelloWorld.py  HelloWorld$py.class
> % java HelloWorld$py -classpath /home/ted/jython2.7.0
> Error: Could not find or load main class HelloWorld
>
> Any further suggestions are greatly appreciated.
>
> Thanks!
>
> Ted
>
> PS. In case it helps, here is some info on my environment:
>
> % jython --version
> Jython 2.7.0
> % java -version
> openjdk version "1.8.0_171"
> OpenJDK Runtime Environment (build 
> 1.8.0_171-8u171-b11-0ubuntu0.17.10.1-b11)
> OpenJDK 64-Bit Server VM (build 25.171-b11, mixed mode)
> % uname -srv
> Linux 4.13.0-46-generic #51-Ubuntu SMP Tue Jun 12 12:36:29 UTC 2018
>
>
>
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>
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Sunday, September 30, 2018 10:51 AM, Jeff Allen 
> <ja...@fa...> wrote:
>
>> The normal way to use Jython would be like CPython:
>>
>> $ jython HelloWorld.py
>>
>> That's with an appropriate PATH, of course, or you say explicitly 
>> where the launcher is as part of the command. If you just wanted to 
>> run the the Python code, that would be the way. The compiled 
>> $py.class would only ever live in memory.
>>
>> But maybe you know this and have something more complicated in mind. 
>> You can run the class you made from a Java program (class with 
>> main()) that you write. But you could run the .py file from a Java 
>> program too, and I think more easily. Either way, you need the jython 
>> JAR on the path as Adam says. What do you have in mind that makes you 
>> want to compile it as a separate step like this?
>>
>>
>> Jeff Allen
>>
>> On 29/09/2018 21:13, Ted Larson Freeman via Jython-users wrote:
>>> I have just installed Jython 2.7, and am looking for a simple 
>>> example of compiling a Python script down to a Java .class file. 
>>> Following a suggestion on Stack Overflow, I tried to compile a file 
>>> called HelloWorld.py, which contains this:
>>>
>>> class HelloWorld(object):
>>>     def hello(self):
>>>         print 'Hello, World!'
>>>
>>> if __name__ == '__main__':
>>>     h = HelloWorld()
>>>     h.hello()
>>>
>>> Using these Jython commands (in the same working directory):
>>>
>>> import py_compile
>>> py_compile.compile('HelloWorld.py')
>>>
>>> That produces a file called HelloWorld$py.class, but when I try to 
>>> run it with java from the command line, I get this error:
>>>
>>> Error: Could not find or load main class HelloWorld
>>>
>>> Please let me know what commands I should use.
>>>
>>> Thanks.
>>>
>>> Ted
>